For a progressive wave on a stretched string, state the meaning of amplitude.
Laser light has a wavelength of $690\,\text{nm}$ in a vacuum. Calculate the period of the light wave.
A two-source interference arrangement is shown in Fig. 5.1. Light from a laser falls normally on a double slit. A screen is placed parallel to the double slit. Interference fringes are observed on the screen at distance $D$ from the double slit. The spacing between the centres of the slits is $a$. The light has wavelength $\lambda$. The separation $x$ between the centres of neighbouring bright fringes is measured for different values of distance $D$.
The way $x$ varies with $D$ is shown in Fig. 5.2. The graph has gradient $G$. Determine an expression, in terms of $G$ and $\lambda$, for the slit separation $a$.
The experiment is repeated using slits separated by $2a$. The wavelength of the light remains unchanged. On Fig. 5.2, sketch a graph to show the outcome of this experiment.
Determine an expression, in terms of $G$ and $\lambda$, for the slit separation $a$.
The experiment is repeated using slits separated by $2a$. The wavelength of the light remains unchanged. On Fig. 5.2, sketch a graph to show the outcome of this experiment.